Component Testing & Accessibility

Evaluate Component Testing & Accessibility through feature boundaries, accessible interactions, behavior-focused tests, measured performance, and production failure handling. Add memoization from profiler or React Compiler evidence rather than guesswork.

Build a Complete Mental Model

Evaluate Component Testing & Accessibility through feature boundaries, accessible interactions, behavior-focused tests, measured performance, and production failure handling. Add memoization from profiler or React Compiler evidence rather than guesswork.

Apply It in Production React

Test an original Component Testing & Accessibility example with empty/loading/error states, keyboard-only interaction, a slow network, rapid repeated events, and component unmount/remount cases. Verify behavior with the browser console, React DevTools, tests, and profiler where relevant.

After This Lesson

• Explain the source of truth and component boundary
• Build an example with keyboard and failure states
• Verify one user-visible behavior with a test or profiler

import { render, screen } from '@testing-library/react';
import userEvent from '@testing-library/user-event';
import { expect, test } from 'vitest';
import Counter from './Counter.jsx';

test('increments from an accessible button', async () => {
  const user = userEvent.setup();
  render(<Counter />);
  await user.click(screen.getByRole('button', { name: /add/i }));
  expect(screen.getByText('Count: 1')).toBeInTheDocument();
});

1 test passed

React Testing Library Introduction — Testing Library